Cryptology ePrint Archive: Report 2014/515

Ideal Social Secret Sharing Using Birkhoff Interpolation Method

Nasrollah Pakniat and Ziba Eslami and Mehrdad Nojoumian

Abstract: The concept of social secret sharing (SSS) was introduced in 2010 by Nojoumian et al. [1,2]. In this scheme, the number of shares allocated to each party depends on the players reputation and the way he interacts with other parties. In other words, weights of the players are periodically adjusted such that cooperative participants receive more shares compared to non-cooperative parties. As our contribution, we propose an ideal social secret sharing (Ideal-SSS) in which the size of each player’s share is equal to the size of the secret. This property will be achieved using hierarchical threshold secret sharing rather than weighted secret sharing. We show that the proposed scheme is secure in a passive adversary model. Compared to SSS, our proposed scheme is more efficient in terms of the share size, communication complexity and computational complexity of the “sharing” protocol. However, the “social tuning” and “reconstruction” protocols of SSS are computationally more efficient than those of the proposed scheme. Depending on the number of execution of social tuning protocol, this might be a reasonable compromise because the reconstruction protocol is executed only once throughout the secret’s lifetime.